Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.
The distribution of electrical power across an electricity grip from a generation site to a consumption site typically occurs by way of a high voltage AC signal that is conveyed by a plurality of coextensive conductors that are suspended on distribution structures such as poles, towers and the like. It is also known to use a neutral conductor that coextends with the other conductors for providing a common reference across the grid. Each, or most of, the structures provide an earth link for the neutral conductor by way of an earth stake that is electrically connected to the neutral conductor. This is referred to as a multiple carting neutral system (MEN) and it provides a convenient means for providing fault protection for the grid and protection of the assets within that grid, as well as protection for those persons who come into contact with those structures.
At a location close to the consumption site, the voltages are transformed to a lower AC voltage that is typically delivered to the site over two wires for a single phase system—an active and a neutral—or four wires for a three phase system—three actives and a neutral. At the consumption site use is made of a separate earth which is often referenced from an earth stake at that site. The neutral conductor is also tied to that earth.
A variety of protection devices have been developed for detecting and protecting against a fault condition associated with a mains wiring systems for commercial and domestic sites such as the consumption site referred to above. These devices generally detect an over-current condition, in that the current in the active conductor exceeds a predetermined threshold, or increases at a rate that suggests there is a low resistance current path between the active conductor and one or both of the neutral or earth conductors.
Notwithstanding these protection devices, there are still many electrocutions and electric shocks that occur due to electrical faults, whether those faults arise from the wiring used at the consumption site, the electrical appliance, the conditions of use of the appliance, or a combination of those factor. As it turns out, the most common form of electrocution is due to a person creating a conductive path between the active conductor and the earth.